Synthesis of aliphatic polyamines

ABSTRACT

An improved process for selectively forming aliphatic polyamines from aliphatic polynitriles having 2 to 3 atoms between cyano groups by reacting aliphatic polynitrile, with hydrogen in the presence of a primary or secondary amine, through a fixed bed reactor while continuously contacting the reactants with granular Raney cobalt packed therein.

BACKGROUND OF THE INVENTION

The present invention relates to an improved process for formingnon-cyclic, aliphatic compounds having a multiplicity of primary aminogroups and forming these compounds in high yields and selectivity fromthe corresponding polynitrile having from 2 to 3 atoms between the cyanogroups.

The hydrogenation of nitriles to amines using conventional hydrogenationcatalysts is well known. However, it is recognized that this syntheticmode is not an effective process for forming noncyclic, aliphaticcompounds from polynitrile having an atomic structure capable of formingfive and six membered ring containing compounds. In such cases thepresently known hydrogenation processes provide noncyclic products inlow selectivity and yield. This is especially true with polynitrilessuch as nitrilotriacetonitrile, iminodiacetonitrile andethylenediaminetetraacetonitrile. Normally, the dominant products formedare cyclic polyamines. When one attempts to adjust the reactionconditions to those which may provide higher selectivity or yield of thenon cyclic, aliphatic compound, one observes rapid inactivation of thecatalyst materials used.

It is generally known that hydrogenation of nitriles can be accomplishedby many modes such as by a batch process using an autoclave or bycontinuous process using a fixed bed reactor to contact a hydrogenationcatalyst with a solution containing a nitrile. The reaction product isgenerally a mixture of primary, secondary and tertiary amines. Theformation of the later two amines are thought to be due to the reactionof an imine intermediate with some of the primary amine product presentin the reaction zone to produce a secondary amine, and in turn, thereaction of the imine with some of the secondary amine to form atertiary amine product. When the starting nitrile has a multiplicity ofcyano groups which are separated by an appropriate chain length of about2 to 3 atoms, the secondary and tertiary amine formation tends to beintramolecular to provide cyclic compounds as the dominate product.Thus, when a dinitrile, such as iminodiacetonitrile, is subjected toconventional hydrogenation, one forms the cyclic compound, piperazine,as the major material. For a trinitrile, such as nitrilotriacetonitrile,the difficulty of forming the corresponding linear aliphatic amine,tris(2-aminoethyl) amine, increases geometrically. Thus, contacting of apolynitrile with a hydrogenation catalyst is a recognized route forproducing cyclic polyamines.

U.S. Pat. Nos. 3,565,957 and 3,733,325 teach that the yields of thecyclic amine can be optimized by carrying out the reaction in thepresence of large amounts of ammonia. By using a hydrogenation catalystin the absence of ammonia to increase the yield of linear product, oneproduces a solid material which inactivates the catalyst in a very shortperiod of time. The short life of the catalyst as well as lowselectivity and yield has caused this process to be deemed economicallyunfeasible in commercially providing linear polyamines.

In all of the hydrogenation processes that are used in convertingpolynitriles to polyamines one requires using a solution of the initialpolynitrile in an inert solvent. Materials which are known to be usefulas inert solvents are alcohols, amides, and ethers as they do notinteract with the other materials in the reaction zone to detract fromthe overall yield and selectivity of the products being formed. When theproduct desired is a cyclic amine, ammonia has, in certain instances,been utilized as a solvent or cosolvent for the process. It has beenthought that due to the reactivity of the imine intermediate productwith amine groups one should not utilize amine materials as the solventin such processes as they would tend to interact with the imine to forma condensation reaction product and detract from the overall selectivityof the desired materials.

It is highly desired to find an economically feasible process forforming, in high selectivity and yield, non-cyclic aliphatic polyaminesfrom corresponding polynitriles. The formed linear polyamines have knownusefulness as chelating and sequestering agents and as reagents in theformation and crosslinking of polymeric products, such as polyurethanesand the like.

SUMMARY OF THE INVENTION

A continuous process for forming an aliphatic polyamine from apolynitrile selected from nitrilotriacetonitrile, iminodiacetonitrileand ethylenediaminetetraacetonitrile. The process provides aliphaticpolyamines in high selectivity and high yields while not adverselyaffecting the catalyst activity or life. The process is thus aneconomical and technical advance over conventional processes.

The present process requires contacting of a polynitrile having itscyano groups separated by from 2 to 3 atoms, with granular Raney cobaltunder a hydrogen pressure of from 500 to 10,000 psi in the presence of aprimary or secondary amine which is introduced as part of the feedmaterial. The process must be carried out in a fixed bed reactor havingRaney cobalt as its packing and passing the reactants through thereaction zone in a manner to have a high ratio of Raney cobalt topolynitrile present, preferably in a trickle bed mode.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a process which uses a combinationof specific parameters to unexpectedly provide a means of formingaliphatic primary amines in high conversion and selectivity frompolynitriles.

The process involves contacting, in a fixed bed reactor, a polynitrileand hydrogen with granular Raney cobalt. The polynitrile can be selectedfrom compounds having at least two cyano groups separated by animmediate chain of 2 or 3 atoms. The cyano groups may be separated byhydrocarbon chains which are saturated or contain olefinic (ethylenic)unsaturation therein or may contain a heteroatom such as nitrogen,oxygen, sulfur, and the like or combinations thereof. Specifically, themost applicable polynitriles are nitrilotriacetonitrile,iminodiacetonitrile and ethylenediaminetetraacetonitrile as thesematerials provide highly desired noncyclic polyamines in an economicalmanner. Other polynitriles include oxidiacetonitrile,thiodiacetonitrile, 2-methylglutaronitrile and 1,3-dicyanopropene. Thesecompounds are normally viewed as having the proper atom chain length tointramolecularly react and form stable cyclic compounds as the dominantproduct. However, the present process provides a means to cause thedominant product to be an aliphatic, non-cyclic polyamine.

The polynitrile reactant must be introduced into the reaction zoneaccording to the present process in the presence of an organic primaryor secondary amine moderating compound or mixtures thereof. In contrastto conventional processes where inorganic ammonia is introduced in largeamounts to achieve high selectivity towards the cyclic amine product,one presently achieves high conversion and selectivity of thepolynitrile to the non-cyclic, aliphatic amine product. It is alsorealized that conventional processes normally contain some primary aminecompound as formed product in the reaction zone but these processes donot inhibit conversion of polynitrile to the cyclic product to providethe high yield (the product of conversion and selectivity) of thepresently desired non-cyclic, aliphatic amine, as is presently achieved.

The amine moderator must be introduced as part of the liquid feed inconjunction with the polynitrile reactant. The amine may be contained ina liquid which is a co-solvent for both the polynitrile and the amine.Alternately, the amine may be used as the solvent for the polynitrile.The amine moderator should be introduced into the reaction zone in atleast about 5 weight percent based on the weight of the polynitrilefeed. It may be present in excess of the polynitrile and may be thesolvent in which the nitrile is contained in concentrations, asdescribed herein below. Any amine may be selected which contains atleast one primary or secondary amino group, is capable of remainingliquid under reaction zone conditions, is mutually soluble with theother liquid feed material or is soluble in a cosolvent used to carrythe feed materials into the reaction zone and is substantially free ofother chemical moieties which may interact with the reactants orproducts in the reaction zone. Examples of suitable amines includemonoamines such as butylamine, pentylamine, heptylamine and the like orpolyamines, such as ethylenediamine, triethylenetetramine,tetraethylenepentamine and the like as well as mixtures thereof.Although it is not preferred, polyamines having four to six atomsbetween terminal amino groups may be used as part of the aminemoderator. For example, one may wish to use a portion of the productamine of the present process as an amine moderator due to its readyavailability and lack of requirement of added storage facilities. Thepreferred amine moderators are the polyamines with ethylenediamine beingthe most preferred as it is a strong solvent for the polynitrilereactants.

The polynitrile must be introduced into the reaction zone as a liquidand, therefore, is normally introduced as a solution in a solventmedium. As stated above, the amine moderator may act as the solvent forthe polynitrile or it may be introduced as part of the polynitrilesolution while using a cosolvent. Cosolvents suitable for this purposeinclude alcohols such as methanol, ethanol, isopropanol, n-butanol andthe like; amides such as N,N-dimethylacetamide, formamide,N,N-dimethylformamide and the like; ethers such as dioxane and the likeas well as other solvents which are inert to the reactants and theproducts in the reaction zone and are capable of remaining liquid underthe reaction conditions. It is preferred that the polynitrile beintroduced as a solution at concentrations of from 5 wt. percent tosaturation, preferably from 5 to 30 wt. percent based on the totalweight of the liquid solution introduced into the reaction zone.

It is understood that the specific polynitrile reactant chosen willdetermine the primary amine product to be formed. Each cyano group willbe converted to a primary methyleneamine group. It has been found thatwhen using the present process, the hydrogenation selectivity goes tothe formation of primary amine product without any major interactionbetween the formed methyleneamine and the intermediate imine groups andespecially substantially low intramolecular reaction.

The catalyst required to perform the present process is granular Raneycobalt. The catalyst is formed from an initial alloy which contains fromabout 50 to 70 wt. percent aluminum, from about 30 to 50 wt. percentcobalt, from 0 to about 6 wt.% chromium and from 0 to about 6 wt.percent molybdenum. Chromium and/or molybdenum may also be provided bytreating the surface of an already activated alloy with a salt of thesematerials to provide from 0 to about 5 percent of these metals on theRaney cobalt surface. The most preferred catalyst is formed from alloyshaving small amounts (0.5 to 5 wt. percent) of chromium and/ormolybdenum.

The catalyst is prepared by contacting the starting alloy with anaqueous alkaline solution formed from an alkali or alkaline earth metalhydroxide, preferably sodium hydroxide. The alloy should be granular,that is have a particle size of from about 0.02 to 0.5 inch andpreferably from about 0.05 to 0.4 inch mean diameter. The activation iscarried out in known manners by contacting the starting alloy withdilute, normally from about 1 to 10 wt. percent, preferably from 1 to 5wt. percent, of an alkaline solution while maintaining a low temperaturesuch as below about 50° C. and preferably below 40° C. Generally, it isbest to activate the alloy at from about 20° to 40° C. Activation isreadily monitored by the evolution of hydrogen and provides a suitablecatalyst for use in the present process when from 20 to 40 percent ofthe aluminum is removed. The activated Raney cobalt catalyst is washedwith water to free it from the alkaline solution and used immediately orstored under water or other inert atmosphere.

The process is carried out by using a fixed bed reactor packed with theabove-described granular Raney cobalt catalyst through which thepolynitrile reactant and primary amine moderator are passed. Thepolynitrile should be introduced into the packed reactor as part of theliquid feed at a flow rate of from about 0.02 to 10 and preferably from0.05 to 2 grams of polynitrile/min-cm². Amine, polynitrile and, whereapplicable, solvent should be maintained in a liquid state in thereaction zone. The liquids should be introduced and flow concurrentlythrough the reactor. Preferably, hydrogen gas is introduced and causedto pass through the reaction zone concurrently with the liquids. Thegranular and high surface area characteristics required of the catalyst,when combined with the relatively low flow rate discussed above,provides the required very high ratio of catalyst surface area topolynitrile reactant.

The contacting of the various materials in the reaction zone is mostpreferably done under trickle bed conditions in which the gaseousmaterial is in a continuous phase while the liquid and solid materialstherein are in a discontinuous phase. The term "trickle bed" used hereinand in the appended claims refers to this 3-phase system and tovelocities of the reactants flowing through the reaction zone which arecapable of maintaining this 3-phase system with the gaseous material asthe continuous phase. It is preferred that the liquid primary orsecondary amine as well as any inert solvent used and the gaseoushydrogen be all permitted to flow concurrently with the polynitrile.Various descriptions have been made about this mode of contact including"Gas-Liquid-Solid Reactor Design" by Shah (1979); "Catalytic ReactorDesign" by Tarhan (1983); and "Hydrodynamics and Solid-Liquid ContactingEffectiveness in Trickle-Bed Reactors", by Gianetto et al AIChE Journal,Vol. 24, No. 6 page 1087.

The polynitrile is contacted with the granular Raney cobalt catalyst inthe presence of hydrogen and a liquid amine as described above. Thehydrogen gas is introduced into the reaction zone at a rate sufficientto maintain a hydrogen pressure in the reaction zone of from 500 to10,000 psi, preferably from 2,000 to 5,000 psi and most preferably from2,500 to 4,000 psi. The amine moderator utilized in the present processmust be introduced into the reactor as part of the liquid feed andpermitted to flow concurrently with the polynitrile. The amine should bepresent in the reaction zone in at least 5% by weight based on theweight of the polynitrile and may be present in excess of thepolynitrile including being the solvent media for the polynitrile.

The reaction zone should be maintained at an elevated temperature offrom 50° to about 150° with from 70° to 120° C. being preferred. Thepressure maintained in the reaction zone should be sufficient tomaintain all of the reactants, the polynitrile, the primary or secondaryamine monitor and the solvent in a liquid state as described above. Thehydrogen pressure described above may be supplemented by partialpressure formed from an inert gas such as nitrogen.

The liquids are preferable introduced into the reaction zone along withthe hydrogen gas in a manner to cause them to flow concurrently,preferably in downward direction. The hydrogen is introduced in a volumeflow rate of from 100 to about 3,000, preferably from 300 to 2,000standard cubic centimeter per minute-centimeter square (scc/min-cm²) anda total liquid volumetric flow ranging from 0.1 to about 50 preferablyfrom 0.2 to about 4 cc/min-cm². These rates have presently been found toprovide sufficient flow of the polynitrile over the Raney cobaltcatalyst to aid in providing a high catalyst to nitrile ratio. Theresidence time should be sufficient to produce an aliphatic polyamine asthe dominant reaction product. A residence time of from about 2 to 10minutes, preferably from 5 to 8 minutes is normally sufficient.

The following examples are given for illustratively purposes only andare not meant to be a limitation on the present invention except asdefined by the claims appended hereto. All parts and percentages are byweight unless otherwise stated.

EXAMPLE 1

Hydrogenation of nitrilotriacetonitrile (NTAN) was carried out using atrickle bed tubular reactor fabricated from 316 stainless steel tubingof 3/8" inside diameter and about 36" long. The reactor was positionedvertically with an inlet feed tube located at its top for each of thefeed materials to be supplied through high pressure pumps and thepressure controlled by a back pressure regulator. The reactor was packedgranular Raney cobalt to provide a bed void fraction of about 0.3 andmaintained at 100° C.

The granular Raney cobalt catalysts were prepared by treating granularalloys of aluminum, cobalt and chromium (60/38/2) of about 6 to 8 mesh(U.S. standard size) with dilute solutions of sodium hydroxide (about 5wt. %) at a temperature of 35°±2° C. while monitoring the hydrogen gasevolution. The hydrogen gas evolution was used to measure the degree andextent of activation of the alloy. The activation was continued untilabout 30% of the original aluminum in the alloy was removed (based on1.5 moles of hydrogen per mole of aluminum). The activated granules werewashed with deionized water to a pH of 7.8 and then used immediately orstored under water.

NTAN was introduced at a liquid flow rate of 0.66 ml/min rate of 1 g/mininto the tubular reactor as a 10 wt. % solution in ethylenediamine.Hydrogen was currently fed into the reactor with the NTAN at a rate of220 scc/min. The reactor pressure was maintained at about 2,800 psi.

The reactor products were analyzed by gas-liquid chromotography and itwas determined that there was 100 percent conversion of the polynitrilewith molar selectivity to the desired linear tris(aminoethyl)amine(TREN) being 80% with only about 20% cyclic aminoethylpiperazine (AEP)formed. The catalyst exhibited good stability and extended activity.

EXAMPLE 2

For comparative purposes, the process described in Example 1 above wasrepeated except that the primary amino solvent, ethylenediamine, wasreplaced by using an equal amount of N,N-dimethylacetamide (DMAC). Thematerial was again analyzed in the same manner using gas-liquidchromotography. It was determined that conversion was only about 80% andthe selectivity of the products was down to about 60% for the linearproduct. In addition, the catalyst became inactive after only a shortperiod of 1 day or less.

EXAMPLE 3

The process described in Example 1 above was repeated except that thesolvent monitor used was tetraethylenepentamine instead ofethylenediamine. The products were analyzed and the conversion wasdetermined to be about 100% with selectivity to the linear product,TREN, being about 70% while the cyclic product was only 30%.

EXAMPLE 4

The process described in Example 1 was repeated except that thepolynitrile reactant was iminodiacetonitrile. The products were analyzedby gas-liquid chromatography and the conversion was determined to beabout 100 percent with 85 percent selectivity to the linear product,diethylenetriamine.

EXAMPLE 5

The process described in Example 1 is repeated except that thepolynitrile reactant is ethylenediaminetetraacetonitrile. The productsare analyzed and the conversion of the polynitrile and the selectivityto the linear product, tetrakis(2-aminoethyl)ethylenediamine, aresubstantially the same values achieved in Example 4 above.

The above examples are given for illustrative purposes only and are notmeant to be a limitation on the subject process nor the claims appendedhereto.

We claim:
 1. A process of converting polynitriles to non-cyclic,aliphatic compounds having a plurality of primary amino groupscomprising, in a fixed-bed reactor maintained at a temperature of fromabout 50° C. to about 150° C. and having granular Raney cobalt packingtherein, introducing into the reactor an aliphatic polynitrile havingcyano groups directly separated by from 2 to 3 atoms in conjunction withat least about 5 weight percent based on the polynitrile of a liquidprimary or secondary amine containing compound, contacting thepolynitrile with the Raney cobalt in the presence of hydrogen pressureof from about 2000 to 10,000 psi for a time sufficient to producenon-cyclic, aliphatic compounds having a plurality of primary aminogroups as the dominant product and recovering said aliphatic polyamines.2. The process of claim 1 wherein said polynitrile in said reactor ismaintained at a flow rate of from 0.02 to 10 gm of polynitrile permin-cm² and said polynitrile, amine, hydrogen and Raney cobalt aremaintained in said reactor under trickle bed conditions.
 3. The processof claim 1 wherein the hydrogen and amine are passed through the reactorconcurrently with the polynitrile; that the hydrogen flow rate is from100 to 3,000 scc/min-cm² ; the hydrogen pressure is at least about 2000psi; and the total liquid flow rate is from 0.1 to 50 cc/min-cm².
 4. Theprocess of claim 2 wherein the hydrogen is passed through the reactorconcurrently with the polynitrile; that the hydrogen flow rate is from100 to 3,000 scc/min-cm² ; the hydrogen pressure is at least about 2000psi; and the total liquid flow rate is from 0.1 to 50 cc/min-cm².
 5. Theprocess of claim 1 wherein the Raney cobalt has a particle size of from0.025 to 0.5 inch mean diameter and is formed by removal of from 20 to40% of the aluminum from an initial alloy composed of about 50 to 70 wt.% aluminum, about 30-50 wt. % cobalt, 0 to about 6 wt. % chromium and 0to about 6 wt. % molybdenum.
 6. The process of claim 2 wherein the Raneycobalt has a particle size of from 0.025 to 0.5 inch mean diameter andis formed by removal of from 20 to 40% of the aluminum from an initialalloy composed of about 50 to 70 wt. % aluminum, about 30-50 wt. %cobalt, 0 to about 6 wt. % chromium and 0 to about 6 wt. % molybdenum.7. The process of claim 3 wherein the Raney cobalt has a particle sizeof from 0.025 to 0.5 inch mean diameter and is formed by removal of from20 to 40% of the aluminum from an initial alloy composed of about 50 to70 wt. % aluminum, about 30-50 wt. % cobalt, 0 to about 6 wt. % chromiumand 0 to about 6 wt. % molybdenum.
 8. The process of claim 1 wherein thereactor is maintained at a temperature of from about 70° C. to about120° C.; the polynitrile is introduced into the reactor at a flow rateof from 0.05 to 2 gm/min-cm² ; the amine forms the solvent medium forthe polynitrile solution; and the hydrogen pressure is from about 2000to 5000 psig.
 9. The process of claim 2 wherein the reactor ismaintained at a temperature of from about 70° C. to about 120° C.; thepolynitrile is introduced in the reactor at a flow rate of from 0.05 to2 gm/min-cm² ; the amine forms the solvent medium for the polynitrilesolution; and the hydrogen pressure is from about 2000 to 5000 psig. 10.The process of claim 1 wherein the polynitrile is nitrilotriacetonitrileand the major recovered product is tris(2-aminoethyl) amine.
 11. Theprocess of claim 2 wherein the polynitrile is nitrilotriacetonitrile andthe major recovered product is tris(2-aminoethyl) amine.
 12. The processof claim 6 wherein the polynitrile is nitrilotriacetonitrile and themajor recovered product is tris(2-aminoethyl) amine.
 13. The process ofclaim 9 wherein the polynitrile is nitrilotriacetonitrile and the majorrecovered product is tris(2-aminoethyl) amine.
 14. The process of claim1 wherein the polynitrile is iminodiacetonitrile and the major recoveredproduct is diethylenetriamine.
 15. The process of claim 2 wherein thepolynitrile is iminodiacetonitrile and the major recovered product isdiethylenetriamine.
 16. The process of claim 6 wherein the polynitrileis iminodiacetonitrile and the major recovered product isdiethylenetriamine.
 17. The process of claim 9 wherein the polynitrileis iminodiacetonitrile and the major recovered product isdiethylenetriamine.
 18. The process of claim 1 wherein the polynitrileis ethylenediaminetetraacetonitrile and the major recovered product istetrakis(2-aminoethyl) ethylenediamine.
 19. The process of claim 2wherein the polynitrile is ethylenediaminetetraacetonitrile and themajor recovered product is tetrakis(2-aminoethyl) ethylenediamine. 20.The process of claim 6 wherein the polynitrile isethylenediaminetetraacetonitrile and the major recovered product istetrakis(2-aminoethyl) ethylenediamine.
 21. The process of claim 9wherein the polynitrile is ethylenediaminetetraacetonitrile and themajor recovered product is tetrakis(2-aminoethyl) ethylenediamine. 22.The process of claim 1 wherein the granular Raney cobalt alloy is of aparticle size of from about 0.05 to 0.4 inch mean diameter and containsup to 5 wt. percent chromium, the liquid amine is present in a molarexcess to the polynitrile reactant and is selected from ethylenediamineand tetraethylenepentamine, the hydrogen pressure is from 2,500 to 4,000psi, the polynitrile reactor flow rate is from 0.05 to 2 g ofpolynitrile/min-cm², the reactor temperature is maintained at from about70° C. to 120° C. and the hydrogen, amine and polynitrile flowconcurrently through the reactor.
 23. The process of claim 2 wherein thegranular Raney cobalt alloy is of a particle size of from about 0.05 to0.4 inch mean diameter and contains up to 5 wt. percent chromium, theliquid amine is present in a molar excess to the polynitrile reactantand is selected from ethylenediamine and tetraethylenepentamine, thehydrogen pressure is from 2,500 to 4,000 psi, the polynitrile reactorflow rate is from 0.05 to 2 g of polynitrile/min-cm², the reactortemperature is maintained at from about 70° C. to 120° C. and thehydrogen, amine and polynitrile flow concurrently through the reactor.24. The process of claim 6 wherein the granular Raney cobalt alloy is ofa particle size of from about 0.05 to 0.4 inch mean diameter andcontains up to 5 wt. percent chromium, the liquid amine is present in amolar excess to the polynitrile reactant and is selected fromethylenediamine and tetraethylenepentamine, the hydrogen pressure isfrom 2,500 to 4,000 psi, the polynitrile reactor flow rate is from 0.05to 2 g of polynitrile/min-cm², the reactor temperature is maintained atfrom about 70° C. to 120° C. and the hydrogen, amine and polynitrileflow concurrently through the reactor.
 25. The process of claim 9wherein the granular Raney cobalt alloy is of a particle size of fromabout 0.05 to 0.4 inch mean diameter and contains up to 5 wt. percentchromium, the liquid amine is present in a molar excess to thepolynitrile reactant and is selected from ethylenediamine andtetraethylenepentamine, the hydrogen pressure is from 2,500 to 4,000psi, the polynitrile reactor flow rate is from 0.05 to 2 g ofpolynitrile/min-cm², the reactor temperature is maintained at from about70° C. to 120° C. and the hydrogen, amine and polynitrile flowconcurrently through the reactor.